Problem: Simplify the following expression: $k = \dfrac{p}{8} + \dfrac{p}{9}$
Explanation: In order to add expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $8$ and $9$ $\lcm(8, 9) = 72$ $ k = \dfrac{9}{9} \cdot \dfrac{p}{8} + \dfrac{8}{8} \cdot \dfrac{p}{9} $ $k = \dfrac{9p}{72} + \dfrac{8p}{72}$ $k = \dfrac{9p +8p}{72}$ $k = \dfrac{17p}{72}$